The present invention relates to an improvement in a brake or clutch mechanism in which shoes slidably contact the inner surface of a drum. More particularly, the invention pertains to a booster mechanism for a drum brake or clutch constituted by two sets of actuating devices and shoes disposed in substantially point or line symmetry with each other, or a booster mechanism for a drum brake or clutch in which an actuating device is disposed between one of the respective ends of two shoes adjacently facing each other, and the other ends thereof are pivotally supported.
A drum brake or clutch which employs a booster mechanism as an actuating mechanism therefor has hitherto been known. The known booster mechanism, however, has such disadvantages that the booster member thereof is large in size and weight as well as high in cost. In addition, since the booster member effects only a pivotal motion with respect to a fixing member, it is disadvantageously difficult to employ the booster mechanism for a floating type shoe.